1. Field of Invention
This invention relates to non-pneumatic tires and, more particularly, to a ribbed or spoked non-pneumatic tire provided with vibration reducing features.
2. Description of the Related Art
Recently, much emphasis has been placed on vehicle fuel efficiency which has fostered intensive research for the purpose of reducing vehicle weight and, in turn, reducing vehicle fuel requirements. One aspect of vehicle design that has received particular attention is the size and weight of the typical spare tire carried in a vehicle for emergency use in replacing flat or defective pneumatic tires.
While the advent of the mini-spare tire has lowered the size and weight of the typical spare tire carried in most vehicles, the non-pneumatic tire holds even more promise for reducing weight and volume. Non-pneumatic tires have been used as industrial tires, off-the-road tires, bicycle tires, wheel barrow tires, and the like. They have not been completely satisfactory in many of these applications because they have not had suitable cushioning and handling characteristics. Also, where the non-pneumatic tires have been solid tires, heat buildup and subsequent degradation of the elastomeric materials comprising the tire body, have limited the uses of such solid non-pneumatic tires.
Ribbed or spoked constructions of non-pneumatic tires have been developed that appear to alleviate many of these drawbacks. One recent development of a non-pneumatic tire by Uniroyal, Inc. comprises an annular body of resilient elastomeric material including an outer cylindrical member and a coaxial, coextensive, inner cylindrical member for mounting on a wheel rim. The outer cylindrical member is supported and cushioned by circumferentially spaced-apart rib members and one or more web members. The rib members extend generally axially of and alongside the web member. The web member lies in a plane that is perpendicular to the rotational axis of the tire. The inner and outer cylindrical members, rib members, and web members are integral with one another.
The purpose of the web and rib members is to provide a load-carrying structure that absorbs bumps during operation of a tire over a road surface.
One of the problems, however, with ribbed or spoked non-pneumatic tires is that unacceptably high levels of noise and vibration are produced by many of the current generation of spoked non-pneumatic tires. While it is somewhat desirable to provide a spare tire that produces relatively higher levels of road noise for the purpose of reminding the driver that the spare tire should be replaced with a conventional pneumatic tire, the level of noise and vibration must still be held to an acceptable level to avoid unnecessarily disturbing the passengers inside the vehicle.
Accordingly, a primary object of this invention is to provide a non-pneumatic tire having a load-carrying and cushioning structure that does not cause unacceptable levels of noise or vibration during vehicle operation.
Another object of this invention is to provide a non-pneumatic tire with radial ribs supporting an outer tread surface that incorporates various structural features to reduce noise and vibration caused by the non-pneumatic tire during vehicle operation.
A further object of this invention is to provide a non-pneumatic tire with a tread surface that provides adequate traction and is specifically structured to reduce vibration during vehicle operation.
Further objects and advantages of this invention will become apparent from the following description.